Method of treating barium titanate

ABSTRACT

Barium titanate is upgraded by chemically treating the raw powder with acetic acid, ammonium hydroxide, or distilled water. This invention relates in general to a method of upgrading the dielectric characteristics of ferroelectric materials and in particular to a method of upgrading commercial barium titanate.

United States Patent [191 Frey et al.

Feb. 27, 1973 METHOD OF TREATING BARIUM TITANATE [75] Inventors: Dennis L. Frey, Metuchen; Sam Divita, West Long Branch; Edward J. Smoke, Edison, all of NJ.

[73] Assignee: The United States of America as represented by the Secretary of the Army [22] Filed: June 23, 1971 [21] Appl. No.: 156,044

[52] US. Cl. ..423/81, 423/69, 423/155,

423/598 [51] Int. Cl. ..C0lf 11/00, COlg 23/00 [58] Field of Search....23/51 R; 423/69, 81, 155, 598

[56] I References Cited UNITED STATES PATENTS 2,988,422 6/1961 Walsh ..23/51 R 3,435,104 3/1969 Brandmayr ..23/5l R X OTHER PUBLICATIONS Flaschen, Journal of the American Chemical Society, Vol. 77, 1954, p. 6194 Rosenthal et al., Ceramic Bulletin, Vol. 37, 1958, pp. 370-375.

Primary Examiner-Herbert T. Carter Attorney-Harry M. Saragovitz et al.

[57] ABSTRACT Barium titanate is upgraded by chemically treating the raw powder with acetic acid, ammonium hydroxide, or distilled water.

1 Claim, No Drawings that its expense makes 1 METHOD OF TREATING BARIUM TITANATE BACKGROUND OF THE INVENTION Commercially available barium titanate powders are either of a very high purity and expensive or of a lower purity and less expensive. The high purity form is adequate for various electronic applications such as capacitor dielectrics where a high degree of reliability is desired. The difficulty with the high purity material is dielectric in capacitors.

SUMMARY OF THE INVENTION The general object of this invention is to provide a method of upgrading the dielectric properties of barium titanate. A more particular object of the invention is to provide a method of treating commercially available bariumtitanate powders of a lower purity and less expensive form in such a manner that it will be suitable for use as a dielectric in capacitors.

We have found that we can upgrade barium titanate by chemically treating the raw powder with acetic acid, ammonium hydroxide, or distilled water.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Two commercially available barium titanate powders are used. Their respective oxide compositions are shown in Table I.

TABLE I Chemical Analysis of Raw Barium Titanate Powders POWDER I Purity excludes carbonate content and loss on ignition. Not detected at minimum level of detection shown.

prohibitive its extensive use as a lo Eighty gram batches of each of the barium titanate powders are placed in 600 milliliters of each of the following solutions: 8 molar ammonium hydroxide and 6 molar acetic acid. The respective solutions are stirred for 3 hours. By the next day, the particulate has settled and each of the solutions are decanted. Six hundred milliliters of distilled water is then added to each particulate with stirring for 2 hours. Each particulate is allowed to settle overnight again, the liquid decanted, and the particulate dried.

Distilled water alone is also used for treating each of the barium titanate powders. In such a treatment, the material is boiled for two hours, followed by two distilled water washin s.

Specrmens of eac of the particulates are then TABLE II Chemical dielectric constant dielectric constant Treatment powder I powder II None 2878 2220 Ammonium Hydroxide 3160 3646 Acetic Acid 4175 4394 Distilled Water 3380 4423 Furthermore the dielectric losses of Powders I and II were found to be comparable to losses of conventional barium titanate specimens; i.e., between 1 percent and 2 percent.

We wish it to be understood that we do not desire to be limited to the exact details of manufacture as described, for obvious modifications will occur to a person skilled in the art.

What is claimed is:

i 1. Method of increasing the dielectric constant of barium titanate said method including the steps of:

A. stirring the barium titanate powder for about three hours in a solution selected from the group consisting of 6 molar acetic acid and 8 molar ammonium hydroxide and allowing the resulting particulate to settle;

B. decanting the solution;

C. adding distilled water to the particulate with stirring and again allowing the particulate to settle;

D. decanting the liquid and drying the particulate;

E. pressing the particulate into a disc; and

F. firing the disc at l300 to l,340 C. in a moderate vacuum of about microns. 

